The effect of biomechanical stimulation on osteoblast differentiation of human jaw periosteum-derived stem cells

Salvianolic acid-A alleviates oxidative stress-induced osteoporosis

AIM

Cellular damage induced by oxidative stress contributes to systemic bone disorders leading to osteoporosis. Bone homeostasis regulates the balance between the functions of osteoblasts and osteoclasts. Osteoblast cells are responsible for bone formation and are very sensitive to oxidative stress. Polyphenolic compounds possess the ability to scavenge free radicals, thus reducing intracellular oxidative stress. Natural compounds such as salvianolic acid A (SAL-A) exhibit prominent antioxidant properties. However, its antioxidant role in bone homeostasis is poorly defined. In this study, we aimed to elucidate the potential role of SAL-A in protecting the osteoblasts from H2O2-induced oxidative stress.

MAIN METHODS

Rat osteoblast cells were treated with or without 500 μM H2O2 in the presence or absence of 5 μM and 10 μM of SAL-A. A series of assays such as cell viability by CCK-8 kit, detection of reactive oxygen species by dichlorodihydrofluorescein diacetate (DCFH-DA), mitochondrial membrane potential by JC-1 fluorescence, level of bone mineralization proteins osteocalcin, bone sialoprotein, and alkaline phosphatase by immunocytochemistry studies, were conducted.

KEY FINDINGS

SAL-A protected the rat osteoblast cells from H2O2-induced cytotoxicity by significantly attenuating free radical generation, thus improving cell viability. SAL-A treatment also significantly restored bone mineralization proteins, including osteocalcin, bone sialoprotein, and alkaline phosphatase, which were aggravated by H2O2-induced oxidative stress.

SIGNIFICANCE

The study results provide the role of SAL-A in protecting the osteoblasts from H2O2-induced oxidative stress in rat osteoblast cells by scavenging the free radicals, increasing the cell viability, mineralization, and differentiation of osteoblasts.

Metabolomic characterization of MC3T3-E1pre-osteoblast differentiation induced by ipriflavone-loaded mesoporous nanospheres

This study reports on the metabolic changes accompanying the differentiation of MC3T3-E1 osteoprogenitor cells induced by mesoporous bioactive glass nanospheres (nMBG) loaded with ipriflavone (nMBG-IP). Ipriflavone (IP) is a synthetic isoflavone known for inhibiting bone resorption, maintaining bone density, and preventing osteoporosis. Delivering IP intracellularly is a promising strategy to modulate bone remodeling at significantly lower doses compared to free drug administration. Our results demonstrate that nMBG are efficiently internalized by pre-osteoblasts and, when loaded with IP, induce their differentiation. This differentiation process is accompanied by pronounced metabolic alterations, as monitored by NMR analysis of medium supernatants and cell extracts (exo- and endo-metabolomics, respectively). The main effects include an early-stage intensification of glycolysis and changes in several metabolic pathways, such as nucleobase metabolism, osmoregulatory and antioxidant pathways, and lipid metabolism. Notably, the metabolic impacts of nMBG-IP and free IP were very similar, whereas nMBG alone induced only mild changes in the intracellular metabolic profile without affecting the cells' consumption/secretion patterns or lipid composition. This finding indicates that the observed effects are primarily related to IP-induced differentiation and that nMBG nanospheres serve as convenient carriers with both efficient internalization and minimal metabolic impact. Furthermore, the observed link between pre-osteoblast differentiation and metabolism underscores the potential of utilizing metabolites and metabolic reprogramming as strategies to modulate the osteogenic process, for instance, in the context of osteoporosis and other bone diseases.

The Biphasic Activity of Auricularia Auricula-Judae Extract on Bone Homeostasis through Inhibition of Osteoclastogenesis and Modulation of Osteogenic Activity

Osteoporosis arises from the disturbance of bone homeostasis, a process regulated by osteoblasts and osteoclasts. The treatment and prevention of bone metabolic disorders resulting from an imbalance in bone homeostasis require the use of agents that effectively promote both bone formation and anti-resorptive effects. Therefore, an investigation was carried out to determine the potential of the edible mushroom Auricularia auricula-judae in modulating bone remodeling by inhibiting RANKL-induced osteoclastogenesis and enhancing BMP-2-stimulated osteoblast differentiation. Moreover, this study assessed the mode of action of the Auricularia auricula-judae extracts. The staining of tartrate-resistant acid phosphatase (TRAP), a marker for osteoclast activity, demonstrated that Auricularia auricula-judae water extract (AAJWE) inhibited the formation of multinucleated osteoclasts while exhibiting no cytotoxic effects. The study demonstrated that AAJWE reduced RANKL-induced osteoclast differentiation by inhibiting c-Fos/NFATc1 through the inhibition of ERK and JNK phosphorylation during the RANKL-induced osteoclast differentiation. Moreover, AAJWE exhibited a dose-dependent induction of ALP expression in the presence of BMP-2 during osteoblast differentiation. The AAJWE strengthened BMP-2-induced osteogenesis through the activation of Runx2 and Smad phosphorylation. Therefore, AAJWE emerges as a promising candidate for both prevention and therapy owing to its biphasic effect, which aids in the preservation of bone homeostasis.

Investigation of the physical, chemical, and biological properties of the cockle shell-derived calcium silicate-based pulp capping material: a pilot study

INTRODUCTION

Hard-setting calcium hydroxide-based materials, e.g., Dycal and Life, have been widely used for direct pulp capping. However, various studies have shown undesirable effects such as high solubility and unpredictable dentine bridge formation. Bioceramic, mainly composed of tricalcium and dicalcium silicates, e.g., mineral trioxide aggregate and Biodentine, have provided more desirable physical and biological properties. This study aims to measure the physical properties, chemical properties, and biological response of human dental pulp cells (HDPCs) on three dental pulp-capping materials, Dycal, Life, and cockle shell-derived tricalcium silicate pulp capping material (C-Cap).

METHODS

C-Cap was prepared from cockle shells and rice husk ash. Its chemical composition was identified using X-ray diffractometry. The setting time, flow, solubility, and radiopacity tests were performed following the International Organization for Standardization 6876:2012. pH and calcium ion release were measured. The materials were subjected to an extraction medium at various concentrations and subsequently measured for cytotoxicity and migration on HDPCs, from three healthy, mature permanent teeth from different donors. Osteogenic differentiation was assessed by examining alkaline phosphatase enzyme activity and alizarin red staining assay. The data were tested for a normal distribution. The differences among groups were statistically analyzed using ANOVA and Tukey's multiple comparison test (p < 0.05).

RESULTS

The setting time of each material was approximately 1-2 min. C-Cap showed the lowest solubility (10.27% ± 1.02%) compared to Dycal (12.67% ± 0.94%) and Life (12.74% ± 1.33%), with a significant difference (p < 0.05). All materials exhibited radiopacity ranging from 2.4 to 2.9 mm of aluminum. C-Cap had the highest flow, alkalinity, and calcium ion release. C-Cap was significantly less cytotoxic than Dycal and Life (p < 0.05). The migration of HDPCs cultured in C-Cap extraction medium (27.74% ± 0.12%) was comparable to that in serum-free medium (27.09% ± 0.08%) with a significant difference (p < 0.05). The mineralization by HDPCs maintained in C-Cap extraction medium was significantly higher than those in Dycal and Life extraction mediums with a significant difference (p < 0.05).

CONCLUSIONS

C-Cap, a tricalcium silicate-based pulp capping material has potential for further development. C-Cap exhibited comparable physical properties and superior biological properties when compared to Dycal and Life.

Effects of Different No-Ozone Cold Plasma Treatment Methods on Mouse Osteoblast Proliferation and Differentiation

Background and Objectives: Enhanced osteoblast differentiation may be leveraged to prevent and treat bone-related diseases such as osteoporosis. No-ozone cold plasma (NCP) treatment is a promising and safe strategy to enhance osteoblast differentiation. Therefore, this study aimed to determine the effectiveness of direct and indirect NCP treatment methods on osteoblast differentiation. Mouse osteoblastic cells (MC3T3-E1) were treated with NCP using different methods, i.e., no NCP treatment (NT group; control), direct NCP treatment (DT group), direct NCP treatment followed by media replacement (MC group), and indirect treatment with NCP-treated media only (PAM group). Materials and Methods: The MC3T3-E1 cells were subsequently assessed for cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, and ALP and osteocalcin mRNA expression using real-time polymerase chain reaction. Results: Cell proliferation significantly increased in the NCP-treated groups (DT and PAM; MC and PAM) compared to the NT group after 24 h (p < 0.038) and 48 h (p < 0.000). ALP activity was increased in the DT and PAM groups at 1 week (p < 0.115) and in the DT, MC, and PAM groups at 2 weeks (p < 0.000) compared to the NT group. Calcium deposition was higher in the NCP-treated groups than in NT group at 2 and 3 weeks (p < 0.000). ALP mRNA expression peaked in the MC group at 2 weeks compared to the NP group (p < 0.014). Osteocalcin mRNA expression increased in the MC group at 2 weeks (p < 0.000) and was the highest in the PAM group at 3 weeks (p < 0.000). Thus, the effects of direct (DT and MC) and indirect (PAM) treatment varied, with MC direct treatment showing the most significant impact on osteoblast activity. Conclusions: The MC group exhibited enhanced osteoblast differentiation, indicating that direct NCP treatment followed by media replacement is the most effective method for promoting bone formation.

Evaluation of in vitro osteoblast and osteoclast differentiation from stem cell: a systematic review of morphological assays and staining techniques

Background

Understanding human stem cell differentiation into osteoblasts and osteoclasts is crucial for bone regeneration and disease modeling. Numerous morphological techniques have been employed to assess this differentiation, but a comprehensive review of their application and effectiveness is lacking.

Methods

Guided by the PRISMA framework, we conducted a rigorous search through the PubMed, Web of Science and Scopus databases, analyzing 254 articles. Each article was scrutinized against pre-defined inclusion criteria, yielding a refined selection of 14 studies worthy of in-depth analysis.

Results

The trends in using morphological approaches were identified for analyzing osteoblast and osteoclast differentiation. The three most used techniques for osteoblasts were Alizarin Red S (mineralization; six articles), von Kossa (mineralization; three articles) and alkaline phosphatase (ALP; two articles) followed by one article on Giemsa staining (cell morphology) and finally immunochemistry (three articles involved Vinculin, F-actin and Col1 biomarkers). For osteoclasts, tartrate-resistant acid phosphatase (TRAP staining) has the highest number of articles (six articles), followed by two articles on DAPI staining (cell morphology), and immunochemistry (two articles with VNR, Cathepsin K and TROP2. The study involved four stem cell types: peripheral blood monocyte, mesenchymal, dental pulp, and periodontal ligament.

Conclusion

This review offers a valuable resource for researchers, with Alizarin Red S and TRAP staining being the most utilized morphological procedures for osteoblasts and osteoclasts, respectively. This understanding provides a foundation for future research in this rapidly changing field.

Employing novel biocompatible composite scaffolds with bioglass 58S and poly L-lactic acid for effective bone defect treatment

BACKGROUND

Bioglass materials have gained significant attention in the field of tissue engineering due to their osteoinductive and biocompatible properties that promote bone cell differentiation. In this study, a novel composite scaffold was developed using a sol-gel technique to combine bioglass (BG) 58 S with a poly L-lactic acid (PLLA).

METHODS AND RESULTS

The physiochemical properties, morphology, and osteoinductive potential of the scaffolds were investigated by X-ray diffraction analysis, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results showed that the SiO2-CaO-P2O5 system was successfully synthesized by the sol-gel method. The PLLA scaffolds containing BG was found to be osteoinductive and promoted mineralization, as demonstrated by calcium deposition assay, upregulation of alkaline phosphatase enzyme activity, and Alizarin red staining data.

CONCLUSIONS

These in vitro studies suggest that composite scaffolds incorporating hBMSCs are a promising substitute material to be implemented in bone tissue engineering. The PLLA/BG scaffolds promote osteogenesis and support the differentiation of bone cells, such as osteoblasts, due to their osteoinductive properties.

Plasma Rich in Growth Factors in Bone Regeneration: The Proximity to the Clot as a Differential Factor in Osteoblast Cell Behaviour

The osteogenic differentiation process, by which bone marrow mesenchymal stem cells and osteoprogenitors transform into osteoblasts, is regulated by several growth factors, cytokines, and hormones. Plasma Rich in Growth Factors (PRGF) is a blood-derived preparation consisting of a plethora of bioactive molecules, also susceptible to containing epigenetic factors such as ncRNAs and EVs, that stimulates tissue regeneration. The aim of this study was to investigate the effect of the PRGF clot formulation on osteogenic differentiation. Firstly, osteoblast cells were isolated and characterised. The proliferation of bone cells cultured onto PRGF clots or treated with PRGF supernatant was determined. Moreover, the gene expression of Runx2 (ID: 860), SP7 (ID: 121340), and ALPL (ID: 249) was analysed by one-step real-time quantitative polymerase chain reaction (RT-qPCR). Additionally, alkaline phosphatase (ALPL) activity determination was performed. The highest proliferative effect was achieved by the PRGF supernatant in all the study periods analysed. Concerning gene expression, the logRGE of Runx2 increased significantly in osteoblasts cultured with PRGF formulations compared with the control group, while that of SP7 increased significantly in osteoblasts grown on the PRGF clots. On the other hand, despite the fact that the PRGF supernatant induced ALPL up-regulation, significantly higher enzyme activity was detected for the PRGF clots in comparison with the supernatant formulation. According to our results, contact with the PRGF clot could promote a more advanced phase in the osteogenic process, associated to higher levels of ALPL activity. Furthermore, the PRGF clot releasate stimulated a higher proliferation rate in addition to reduced SP7 expression in the cells located at a distant ubication, leading to a less mature osteoblast stage. Thus, the spatial relationship between the PRGF clot and the osteoprogenitors cells could be a factor that influences regenerative outcomes.

Osteogenic assessment of leukocyte platelet-rich fibrin and injectable platelet-rich fibrin in the human osteosarcoma MG - 63 cell line in chronic periodontitis patients: An in vitro study

Background

The burgeoning interest in implant and regenerative dental care has led to a notable upsurge in the utilization of regenerative modalities. The intent of the present investigation was to evaluate the osteogenic ability of two different concentrated platelet groups at various concentrations in the human osteosarcoma MG-63 cell line.

Materials and Methods

Blood samples from 21 volunteers with chronic periodontitis were collected which were then centrifuged in accordance with the protocols of Choukroun et al. and Miron et al. to produce leukocyte- and platelet-rich fibrin (L-PRF) and injectable platelet-rich fibrin (I-PRF), respectively. Following MG-63 cell culture, the osteogenic ability of 0, 4%, and 20% concentrations of both L-PRF and I-PRF were determined using the real-time polymerase chain reaction assay.

Results

The results showed that 20% I-PRF (1.52 ± 0.24) and 4% L-PRF (1.42 ± 0.37) had the highest amount of bone morphogenetic protein 2 and osteocalcin, respectively.

Conclusion

I-PRF appears to promote the initial differentiation of cells.

Bone-Targeted Nanoparticle Drug Delivery System-Mediated Macrophage Modulation for Enhanced Fracture Healing

Despite decades of progress, developing minimally invasive bone-specific drug delivery systems (DDS) to improve fracture healing remains a significant clinical challenge. To address this critical therapeutic need, nanoparticle (NP) DDS comprised of poly(styrene-alt-maleic anhydride)-b-poly(styrene) (PSMA-b-PS) functionalized with a peptide that targets tartrate-resistant acid phosphatase (TRAP) and achieves preferential fracture accumulation has been developed. The delivery of AR28, a glycogen synthase kinase-3 beta (GSK3β) inhibitor, via the TRAP binding peptide-NP (TBP-NP) expedites fracture healing. Interestingly, however, NPs are predominantly taken up by fracture-associated macrophages rather than cells typically associated with fracture healing. Therefore, the underlying mechanism of healing via TBP-NP is comprehensively investigated herein. TBP-NPAR28 promotes M2 macrophage polarization and enhances osteogenesis in preosteoblast-macrophage co-cultures in vitro. Longitudinal analysis of TBP-NPAR28 -mediated fracture healing reveals distinct spatial distributions of M2 macrophages, an increased M2/M1 ratio, and upregulation of anti-inflammatory and downregulated pro-inflammatory genes compared to controls. This work demonstrates the underlying therapeutic mechanism of bone-targeted NP DDS, which leverages macrophages as druggable targets and modulates M2 macrophage polarization to enhance fracture healing, highlighting the therapeutic benefit of this approach for fractures and bone-associated diseases.

Platelet-Rich Plasma Lysate Enhances the Osteogenic Differentiation of Adipose-Derived Stem Cells

ABSTRACT

Adipose-derived stem cells (ADSCs) have become an accepted source of cells in bone tissue engineering. This study aimed to investigate whether platelet-rich plasma (PRP) lysate can replace traditional fetal bovine serum as a culture medium with the enhanced proliferation and osteogenic potential of ADSCs. We divided the experiment into 5 groups where the ADSCs were cultured in an osteogenic medium containing 2.5%, 5%, 7.5%, and 10% PRP lysate with 10% fetal bovine serum as the control group. The cell proliferation, alkaline phosphatase (ALP) activity, ALP stain, alizarin red stain, osteocalcin (OCN) protein expression, and osteogenic-specific gene expression were analyzed and compared among these groups. The outcome showed that all PRP lysate-treated groups had good ALP stain and ALP activity performance. Better alizarin red stains were found in the 2.5%, 5%, and 7.5% PRP lysate groups. The 2.5% and 5% PRP lysate groups showed superior results in OCN quantitative polymerase chain reaction, whereas the 5% and 7.5% PRP lysate groups showed higher OCN protein expressions. Early RUNX2 (Runt-related transcription factor 2 () genes were the most expressed in the 5% PRP lysate group, followed by the 2.5% PRP lysate group, and then the 7.5% PRP lysate group. Thus, we concluded that 5% PRP lysate seemed to provide the optimal effect on enhancing the osteogenic potential of ADSCs. Platelet-rich plasma lysate-treated ADSCs were considered to be a good cell source for application in treating nonunion or bone defects in the future.

Oral fibroblasts rescue osteogenic differentiation of mesenchymal stem cells after exposure to Zoledronic acid in a paracrine effect

Background: Medication-related osteonecrosis of the jaw is a serious complication that develops in oncologic patients treated with Zoledronic acid. Although used for over 30 years, the influence of Zoledronic acid on bone has been thoroughly investigated, mainly on osteoclasts. While decreasing osteoclast differentiation and function, for many years it was thought that Zoledronic acid increased osteoblast differentiation, thus increasing bone volume. Moreover, despite the influence of soft tissue on the bone healing process, the impact of zoledronic acid on the interaction between soft tissue and bone was not investigated. Aim: Our goal was to investigate the influence of Zoledronic Acid and soft tissue cells on osteogenic differentiation of mesenchymal stem cells (MSCs). Materials and methods: Osteogenic differentiation of MSCs was examined after exposure to Zoledronic Acid. To determine the influence of soft tissue cells on MSCs' osteogenic differentiation, conditioned media from keratinocytes and oral fibroblasts were added to osteogenic medium supplemented with Zoledronic Acid. Proteomic composition of keratinocytes' and fibroblasts' conditioned media were analyzed. Results: Zoledronic Acid decreased osteogenic differentiation of MSCs by seven-fold. The osteogenic differentiation of MSCs was restored by the supplementation of fibroblasts' conditioned medium to osteogenic medium, despite Zoledronic acid treatment. Five osteogenic proteins involved in the TGFβ pathway were exclusively identified in fibroblasts' conditioned medium, suggesting their role in the rescue effect. Conclusion: Oral fibroblasts secrete proteins that enable osteogenic differentiation of MSCs in the presence of Zoledronic Acid.

Effect of Ishophloroglucin A Isolated from Ishige okamurae on In Vitro Osteoclastogenesis and Osteoblastogenesis

The balance between bone-resorbing osteoclasts and bone-forming osteoblasts is essential for the bone remodeling process. This study aimed to investigate the effect of Ishophloroglucin A (IPA) isolated from Ishige okamurae on the function of osteoclasts and osteoblasts in vitro. First, we demonstrated the effect of IPA on osteoclastogenesis in receptor activator of nuclear factor κB ligand (RANKL)-induced RAW 264.7 cells. IPA inhibited the tartrate-resistant acid phosphatase (TRAP) activity and osteoclast differentiation in RANKL-induced RAW 264.7 cells. Moreover, it inhibited the RANKL-induced osteoclast-related factors, such as TRAP, matrix metalloproteinase-9 (MMP-9), and calcitonin receptor (CTR), and transcription factors, such as nuclear factor of activated T cells 1 (NFATc1) and c-Fos. IPA significantly suppressed RANKL-activated extracellular signal-regulated kinase (ERK), and NF-κB in RAW 264.7 cells. Our data indicated that the ERK and NF-κB pathways were associated with the osteoclastogenesis inhibitory activity of IPA. Next, we demonstrated the effect of IPA on osteoblastogenesis in MG-63 cells. IPA significantly promoted alkaline phosphatase (ALP) activity in MG-63 cells, along with the osteoblast differentiation-related markers bone morphogenetic protein 2 (BMP2), type 1 collage (COL1), p-Smad1/5/8, and Runx2, by activating the MAPK signaling pathways. Taken together, the study indicated that IPA could be effective in treating bone diseases, such as osteoporosis.

Immuno-histologic and histomorphometric evaluation of Angelica sinensis adjunctive to ß-tricalcium phosphate in critical-sized class II furcation defects in dogs

OBJECTIVE

The study evaluates the effectiveness of Angelica sinensis (As) adjunctive to Beta-tricalcium phosphate (β-TCP) bone graft in the management of induced critical sized class II furcation defects in dogs.

MATERIAL AND METHOD

A randomized study design was conducted on the third and fourth premolars of six dogs. A total of twenty-four defects were surgically created. After reflecting a mucoperiosteal flap, twelve defects were filled with As granules mixed with β-TCP (Experimental group) while the other twelve defects were filled with β-TCP only (Control group) and both were covered by collagen membrane. At the fourth and eighth weeks, jaw segments were dissected and processed for immune-histological examination and histomorphometry analysis.

RESULTS

At four and eight weeks after treatment, experimental group showed a statistically significant increase in the height of newly formed interradicular bone (p = 0.001 and p = 0.0001 respectively), its surface area (p = 0.002 and p = 0.02 respectively), and the thickness of its trabeculae (p = 0.0001 and p = 0.001 respectively), when compared to control group. Moreover. alkaline phosphatase immunoreaction showed higher intensity in the osteoblast cells of experimental group compared to control group.

CONCLUSION

As enhances periodontal regeneration and bone-formation when used in the management of furcation defects.

Mechanical strain induces ex vivo expansion of periosteum

Segmental bone defects present complex clinical challenges. Nonunion, malunion, and infection are common sequalae of autogenous bone grafts, allografts, and synthetic bone implants due to poor incorporation with the patient's bone. The current project explores the osteogenic properties of periosteum to facilitate graft incorporation. As tissue area is a natural limitation of autografting, mechanical strain was implemented to expand the periosteum. Freshly harvested, porcine periosteum was strained at 5 and 10% per day for 10 days with non-strained and free-floating samples serving as controls. Total tissue size, viability and histologic examination revealed that strain increased area to a maximum of 1.6-fold in the 10% daily strain. No change in tissue anatomy or viability via MTT or Ki67 staining and quantification was observed among groups. The osteogenic potential of the mechanical expanded periosteum was then examined in vivo. Human cancellous allografts were wrapped with 10% per day strained, fresh, free-floating, or no porcine periosteum and implanted subcutaneously into female, athymic mice. Tissue was collected at 8- and 16-weeks. Gene expression analysis revealed a significant increase in alkaline phosphatase and osteocalcin in the fresh periosteum group at 8-weeks post implantation compared to all other groups. Values among all groups were similar at week 16. Additionally, histological assessment with H&E and Masson-Goldner Trichrome staining showed that all periosteal groups outperformed the non-periosteal allograft, with fresh periosteum demonstrating the highest levels of new tissue mineralization at the periosteum-bone interface. Overall, mechanical expansion of the periosteum can provide increased area for segmental healing via autograft strategies, though further studies are needed to explore culture methodology to optimize osteogenic potential.

Naphthenic acid fraction components from oil sands process-affected water from the Athabasca Oil Sands Region impair murine osteoblast differentiation and function

The extraction of bitumen from surface mining in the Athabasca Oil Sands Region (AOSR) produces large quantities of oil sands process-affected water (OSPW) that needs to be stored in settling basins near extraction sites. Chemical constituents of OSPW are known to impair bone health in some organisms, which can lead to increased fracture risk and lower reproductive fitness. Naphthenic acid fraction components (NAFCs) are thought to be among the most toxic class of compounds in OSPW; however, the effect of NAFCs on osteoblast development is largely unknown. In this study, we demonstrate that NAFCs from OSPW inhibit osteoblast differentiation and deposition of extracellular matrix, which is required for bone formation. Extracellular matrix deposition was inhibited in osteoblasts exposed to 12.5-125 mg/L of NAFC for 21 days. We also show that components within NAFCs inhibit the expression of gene markers of osteoblast differentiation and function, namely, alkaline phosphatase (Alp), osteocalcin, and collagen type 1 alpha 1 (Col1a1). These effects were partially mediated by the induction of glucocorticoid receptor (GR) activity; NAFC induces the expression of the GR activity marker genes Sgk1 (12.5 mg/L) and p85a (125 mg/L) and inhibits GR protein (125 mg/L) and Opg RNA (12.5 mg/L) expression. This study provides evidence that NAFC concentrations of 12.5 mg/L and above can directly act on osteoblasts to inhibit bone formation and suggests that NAFCs contain components that can act as GR agonists, which may have further endocrine disrupting effects on exposed wildlife.

Effects of erythropoietin on osteoblast in the tooth extraction socket in mice periodontitis model

Periodontitis is an excessive inflammatory event in tooth-supporting tissues and can cause tooth loss. We used erythropoietin (EPO), which has been reported to play an important role in bone healing and modulation of angiogenesis, as a therapeutic agent in vivo and in vitro experimental models to analyze its effect on periodontitis. First, EPO was applied to in vitro MC3T3-E1 cells and human periodontal ligament fibroblast (hPDLF) cells to examine its function in altered cellular events and gene expression patterns. In vitro cultivation of MC3T3-E1 and hPDLF cells with 10 IU/ml EPO at 24 and 48 h showed an obvious increase in cell proliferation. Interestingly, EPO treatment altered the expression of osteogenesis-related molecules, including alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), and osteocalcin (OC) in MC3T3-E1 cells but not in hPDLF cells. In particular, MC3T3-E1 cells showed increased expression of ALP, BMP-2, and OC on day 5, while hPDLF cells showed increased expression of BMP-2, and OC on day 14. Based on the in vitro examination, we evaluated the effect of EPO on bone formation using an experimentally-induced animal periodontitis model. After the induction of periodontitis in the maxillary left second M, 10 IU/ml of EPO was locally applied to the extraction tooth sockets. Histomorphological examination using Masson’s trichrome (MTC) staining showed facilitated bone formation in the EPO-treated groups after 14 days. Similarly, stronger positive reactions against vascular endothelial growth factor (VEGF), cluster of differentiation 31 (CD31), runt-related transcription factor 2 (RUNX2), and osteocalcin (OC) were detected in the EPO-treated group compared to the control. Meanwhile, myeloperoxidase, an inflammatory marker, was decreased in the EPO-treated group on days 1 and 5. Overall, EPO facilitates bone healing and regeneration through altered signaling regulation and modulation of inflammation in the osteoblast cell lineage and to a lesser extent in hPDLF cells.

Progress of Periosteal Osteogenesis: The Prospect of In Vivo Bioreactor

Repairing large segment bone defects is still a clinical challenge. Bone tissue prefabrication shows great translational potentials and has been gradually accepted clinically. Existing bone reconstruction strategies, including autologous periosteal graft, allogeneic periosteal transplantation, xenogeneic periosteal transplantation, and periosteal cell tissue engineering, are all clinically valuable treatments and have made significant progress in research. Herein, we reviewed the research progress of these techniques and briefly explained the relationship among in vivo microenvironment, mechanical force, and periosteum osteogenesis. Moreover, we also highlighted the importance of the critical role of periosteum in osteogenesis and explained current challenges and future perspective.

The Impact of Graphene Oxide on Polycaprolactone PCL Surfaces: Antimicrobial Activity and Osteogenic Differentiation of Mesenchymal Stem Cell

In dentistry, bone regeneration requires osteoinductive biomaterial with antibacterial properties. Polycaprolactone (PCL) may be combined with different nanofillers including reduced graphene oxide (rGO). Here, the amount of rGO filler was defined to obtain a biocompatible and antibacterial PCL-based surface supporting the adhesion and differentiation of human mesenchymal stem cells (MSCs). Compounds carrying three different percentages of rGO were tested. Among all, the 5% rGO-PCL compound is the most bacteriostatic against Gram-positive bacteria. All scaffolds are biocompatible. MSCs adhere and proliferate on all scaffolds; however, 5% rGO-PCL surface supports the growth of cells and implements the expression of extracellular matrix components necessary to anchor the cells to the surface itself. Moreover, the 5% rGO-PCL surface has superior osteoinductive properties confirmed by the improved alkaline phosphatase activity, mineral matrix deposition, and osteogenic markers expression. These results suggest that 5% rGO-PCL has useful properties for bone tissue engineering purposes.

Poly(DL-lactic acid) scaffolds as a bone targeting platform for the co-delivery of antimicrobial agents against S. aureus-C. albicans mixed biofilms

New strategies for the treatment of polymicrobial bone infections are required. In this study, the co-delivery of two antimicrobials by poly(D,L-lactic acid) (PDLLA) scaffolds was investigated in a polymicrobial biofilm model. PDLLA scaffolds were prepared by solvent casting/particulate leaching methodology, incorporating minocycline and voriconazole as clinically relevant antimicrobial agents. The scaffolds presented a sponge-like appearance, suitable to support cell proliferation and drug release. Single- and dual-species biofilm models of Staphylococcus aureus and Candida albicans were developed and characterized. S. aureus presented a higher ability to form single-species biofilms, compared to C. albicans. Minocycline and voriconazole-loaded PDLLA scaffolds showed activity against S. aureus and C. albicans single- and dual-biofilms. Ultimately, the cytocompatibility/functional activity of PDLLA scaffolds observed in human MG-63 osteosarcoma cells unveil their potential as a next-generation co-delivery system for antimicrobial therapy in bone infections.

Electrical stimulation of titanium to promote stem cell orientation, elongation and osteogenesis

Electrical stimulation of cells allows exogenous electric signals as stimuli to manipulate cell growth, preferential orientation and bone remodelling. In this study, commercially pure titanium discs were utilised in combination with a custom-built bioreactor to investigate the cellular responses of human mesenchymal stem cells via in-vitro functional assays. Finite element analysis revealed the homogeneous delivery of electric field in the bioreactor chamber with no detection of current density fluctuation in the proposed model. The custom-built bioreactor with capacitive stimulation delivery system features long-term stimulation with homogeneous electric field, biocompatible, sterilisable, scalable design and cost-effective in the manufacturing process. Using a continuous stimulation regime of 100 and 200 mV/mm on cp Ti discs, viability tests revealed up to an approximately 5-fold increase of cell proliferation rate as compared to non-stimulated controls. The human mesenchymal stem cells showed more elongated and differentiated morphology under this regime, with evidence of nuclear elongation and cytoskeletal orientation perpendicular to the direction of electric field. The continuous stimulation did not cause pH fluctuations and hydrogen peroxide production caused by Faradic reactions, signifying the suitability for long-term toxic free stimulation as opposed to the commonly used direct stimulation regime. An approximate of 4-fold increase in alkaline phosphatase production and approximately 9-fold increase of calcium deposition were observed on 200 mV/mm exposed samples relative to non-stimulated controls. It is worth noting that early stem cell differentiation and matrix production were observed under the said electric field even without the presence of chemical inductive growth factors. STATEMENT OF SIGNIFICANCE: This manuscript presents a study on combining pure titanium (primarily preferred as medical implant materials) and electrical stimulation in a purpose-built bioreactor with capacitive stimulation delivery system. A continuous capacitive stimulation regime on titanium disc has resulted in enhanced stem cell orientation, nuclei elongation, proliferation and differentiation as compared to non-stimulated controls. We believe that this manuscript creates a paradigm for future studies on the evolution of healthcare treatments in the area of targeted therapy on implantable and wearable medical devices through tailored innovative electrical stimulation approach, thereby influencing therapeutic conductive and electroactive biomaterials research prospects and development.

The Neuropeptide Spexin Promotes the Osteoblast Differentiation of MC3T3-E1 Cells via the MEK/ERK Pathway and Bone Regeneration in a Mouse Calvarial Defect Model

BACKGROUND

The neural regulation of bone regeneration has emerged recently. Spexin (SPX) is a novel neuropeptide and regulates multiple biological functions. However, the effects of SPX on osteogenic differentiation need to be further investigated. Therefore, the aim of this study is to investigate the effects of SPX on osteogenic differentiation, possible underlying mechanisms, and bone regeneration.

METHODS

In this study, MC3T3-E1 cells were treated with various concentrations of SPX. Cell proliferation, osteogenic differentiation marker expressions, alkaline phosphatase (ALP) activity, and mineralization were evaluated using the CCK-8 assay, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), ALP staining, and alizarin red S staining, respectively. To determine the underlying molecular mechanism of SPX, the phosphorylation levels of signaling molecules were examined via western blot analysis. Moreover, in vivo bone regeneration by SPX (0.5 and 1 µg/µl) was evaluated in a calvarial defect model. New bone formation was analyzed using micro-computed tomography (micro-CT) and histology.

RESULTS

The results indicated that cell proliferation was not affected by SPX. However, SPX significantly increased ALP activity, mineralization, and the expression of genes for osteogenic differentiation markers, including runt-related transcription factor 2 (Runx2), Alp, collagen alpha-1(I) chain (Col1a1), osteocalcin (Oc), and bone sialoprotein (Bsp). In contrast, SPX downregulated the expression of ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1). Moreover, SPX upregulated phosphorylated mitogen-activated protein kinase kinase (MEK1/2) and extracellular signal-regulated kinase (ERK1/2). In vivo studies, micro-CT and histologic analysis revealed that SPX markedly increased a new bone formation.

CONCLUSION

Overall, these results demonstrated that SPX stimulated osteogenic differentiation in vitro and increased in vivo bone regeneration via the MEK/ERK pathway.

Biophysical Stimuli as the Fourth Pillar of Bone Tissue Engineering

The repair of critical bone defects remains challenging worldwide. Three canonical pillars (biomaterial scaffolds, bioactive molecules, and stem cells) of bone tissue engineering have been widely used for bone regeneration in separate or combined strategies, but the delivery of bioactive molecules has several obvious drawbacks. Biophysical stimuli have great potential to become the fourth pillar of bone tissue engineering, which can be categorized into three groups depending on their physical properties: internal structural stimuli, external mechanical stimuli, and electromagnetic stimuli. In this review, distinctive biophysical stimuli coupled with their osteoinductive windows or parameters are initially presented to induce the osteogenesis of mesenchymal stem cells (MSCs). Then, osteoinductive mechanisms of biophysical transduction (a combination of mechanotransduction and electrocoupling) are reviewed to direct the osteogenic differentiation of MSCs. These mechanisms include biophysical sensing, transmission, and regulation. Furthermore, distinctive application strategies of biophysical stimuli are presented for bone tissue engineering, including predesigned biomaterials, tissue-engineered bone grafts, and postoperative biophysical stimuli loading strategies. Finally, ongoing challenges and future perspectives are discussed.

Evaluating potential of tissue-engineered cryogels and chondrocyte derived exosomes in articular cartilage repair

Treatment of articular cartilage injuries especially osteochondral tissue requires intervention of bioengineered scaffold. In this study, we investigated the potential of the tissue-engineered cryogel scaffold fabricated using cryogelation technology. Two types of cryogels viz. chitosan-gelatin-chondroitin sulfate (CGC) for articular cartilage and nano-hydroxyapatite-gelatin (HG) for subchondral bone were fabricated. Further, novel bilayer cryogel designed using single process fabrication of two layers (CGC as top layer and HG as the lower layer) was designed to mimic osteochondral unit. CGC cryogel was tested for their biocompatibility using the enzymatically isolated chondrcoytes from goat articular cartilage while HG cryogel was tested using pre-osteoblast cell line. Extracellular vesicles, specifically exosomes were isolated from the spent media of chondrocytes to validate their effect over cell proliferation and migration which are required for defect healing and infiltration respectively. These isolated exosomes were characterized and analyzed for confirming their size distribution profile and visualized morphologically using advanced microscopy techniques. For cartilage part, CGC cryogels were examined as delivery system for delivering exosomes at defect site, where 80% of release was observed in 72 h. Release of 18.7 µg chondroitin sulfate/mg cryogel was obtained in a period of one week from CGC cryogel (termed cryogel extract) which has chondroprotective effect. Further, effect of exosome concentration (10 and 20 µg/ml), CGC extract and combination of exosome and CGC extract (Exo-Ex) were assessed over the chondrocytes. In addition, in vitro scratch wound assay was performed to analyse the migration capacity over the micro-injury when treated with exosomes, cryogel extract and Exo-Ex. The overall results thus answer key questions of therapeutic potential of chondrocyte exosomes, cryogel extract in addition to potential of CGC and HG cryogel for osteochondral repair.

Regulation of the integrin αVβ3- actin filaments axis in early osteogenesis of human fibroblasts under cyclic tensile stress

Background

Integrins play a prominent role in osteogenic differentiation by transmitting both mechanical and chemical signals. Integrin expression is closely associated with tensile stress, which has a positive effect on osteogenic differentiation. We investigated the relationship between integrin αVβ3 and tensile stress.

Methods

Human fibroblasts were treated with c (RGDyk) and lentivirus transduction to inhibit function of integrin αVβ3. Y-15, cytochalasin D and verteporfin were used to inhibit phosphorylation of FAK, polymerization of microfilament and function of nuclear YAP, respectively. Fibroblasts were exposed to a cyclic tensile stress of 10% at 0.5 Hz, once a day for 2 h each application. Fibroblasts were harvested on day 4 and 7 post-treatment. The expression of ALP, RUNX2, integrin αVβ3, β-actin, talin-1, FAK, vinculin, and nuclear YAP was detected by Western blot or qRT-PCR. The expression and distribution of integrin αVβ3, vinculin, microfilament and nuclear YAP.

Results

Cyclic tensile stress was found to promote expression of ALP and RUNX2. Inhibition of integrin αVβ3 activation downregulated the rearrangement of microfilament and the expression of ALP, RUNX2 and nuclear YAP. When the polymerization of microfilament was inhibited the expression of ALP, RUNX2 and nuclear YAP were decreased. The phosphorylation of FAK induced by cyclic tensile stress reduced by the inhibition of integrin αVβ3. The expression of ALP and RUNX2 was decreased by inhibition of phosphorylation of FAK and inhibition of nuclear YAP.

Conclusions

Cyclic tensile stress promotes osteogenesis of human fibroblasts via integrin αVβ3-microfilament axis. Phosphorylation of FAK and nuclear YAP participates in this process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02597-y.

Omega-3 fatty acid-rich fish oil supplementation prevents rosiglitazone-induced osteopenia in aging C57BL/6 mice and in vitro studies

Rosiglitazone is an effective insulin-sensitizer, however associated with bone loss mainly due to increased bone resorption and bone marrow adiposity. We investigated the effect of the co-administration of fish oil rich in omega-3 fatty acids (FAs) on rosiglitazone-induced bone loss in C57BL/6 mice and the mechanisms underlying potential preventive effect. Mice fed the iso-caloric diet supplemented with fish oil exhibited significantly higher levels of bone density in different regions compared to the other groups. In the same cohort of mice, reduced activity of COX-2, enhanced activity of alkaline phosphatase, lower levels of cathepsin k, PPAR-γ, and pro-inflammatory cytokines, and a higher level of anti-inflammatory cytokines were observed. Moreover, fish oil restored rosiglitazone-induced down-regulation of osteoblast differentiation and up-regulation of adipocyte differentiation in C3H10T1/2 cells and inhibited the up-regulation of osteoclast differentiation of RANKL-treated RAW264.7 cells. We finally tested our hypothesis on human Mesenchymal Stromal Cells differentiated to osteocytes and adipocytes confirming the beneficial effect of docosahexaenoic acid (DHA) omega-3 FA during treatment with rosiglitazone, through the down-regulation of adipogenic genes, such as adipsin and FABP4 along the PPARγ/FABP4 axis, and reducing the capability of osteocytes to switch toward adipogenesis. Fish oil may prevent rosiglitazone-induced bone loss by inhibiting inflammation, osteoclastogenesis, and adipogenesis and by enhancing osteogenesis in the bone microenvironment.

Osteoprotective Effects of Loganic Acid on Osteoblastic and Osteoclastic Cells and Osteoporosis-Induced Mice

Osteoporosis is a common disease caused by an imbalance of processes between bone resorption by osteoclasts and bone formation by osteoblasts in postmenopausal women. The roots of Gentiana lutea L. (GL) are reported to have beneficial effects on various human diseases related to liver functions and gastrointestinal motility, as well as on arthritis. Here, we fractionated and isolated bioactive constituent(s) responsible for anti-osteoporotic effects of GL root extract. A single phytochemical compound, loganic acid, was identified as a candidate osteoprotective agent. Its anti-osteoporotic effects were examined in vitro and in vivo. Treatment with loganic acid significantly increased osteoblastic differentiation in preosteoblast MC3T3-E1 cells by promoting alkaline phosphatase activity and increasing mRNA expression levels of bone metabolic markers such as Alpl, Bglap, and Sp7. However, loganic acid inhibited osteoclast differentiation of primary-cultured monocytes derived from mouse bone marrow. For in vivo experiments, the effect of loganic acid on ovariectomized (OVX) mice was examined for 12 weeks. Loganic acid prevented OVX-induced bone mineral density loss and improved bone structural properties in osteoporotic model mice. These results suggest that loganic acid may be a potential therapeutic candidate for treatment of osteoporosis.

The Bone-Forming Properties of Periosteum-Derived Cells Differ Between Harvest Sites

The development of alternatives for autologous bone grafts is a major focus of bone tissue engineering. To produce living bone-forming implants, skeletal stem and progenitor cells (SSPCs) are envisioned as key ingredients. SSPCs can be obtained from different tissues including bone marrow, adipose tissue, dental pulp, and periosteum. Human periosteum-derived cells (hPDCs) exhibit progenitor cell characteristics and have well-documented in vivo bone formation potency. Here, we have characterized and compared hPDCs derived from tibia with craniofacial hPDCs, from maxilla and mandible, respectively, each representing a potential source for cell-based tissue engineered implants for craniofacial applications. Maxilla and mandible-derived hPDCs display similar growth curves as tibial hPDCs, with equal trilineage differentiation potential toward chondrogenic, osteogenic, and adipogenic cells. These craniofacial hPDCs are positive for SSPC-markers CD73, CD164, and Podoplanin (PDPN), and negative for CD146, hematopoietic and endothelial lineage markers. Bulk RNA-sequencing identified genes that are differentially expressed between the three sources of hPDC. In particular, differential expression was found for genes of the HOX and DLX family, for SOX9 and genes involved in skeletal system development. The in vivo bone formation, 8 weeks after ectopic implantation in nude mice, was observed in constructs seeded with tibial and mandibular hPDCs. Taken together, we provide evidence that hPDCs show different profiles and properties according to their anatomical origin, and that craniofacial hPDCs are potential sources for cell-based bone tissue engineering strategies. The mandible-derived hPDCs display - both in vitro and in vivo - chondrogenic and osteogenic differentiation potential, which supports their future testing for use in craniofacial bone regeneration applications.

Bone morphogenetic protein 2-enhanced osteogenic differentiation of stem cell spheres by regulation of Runx2 expression

Bone morphogenetic protein 2 (BMP-2) is a growth factor that is used to induce osteogenic differentiation in stem cells. The present study assessed the effects of BMP-2 on stem cell spheroid morphology, viability and osteogenic differentiation. Stem cell spheres were constructed and treated with BMP-2 at predetermined concentrations (0-100 ng/ml) using concave microwells. Cell viability was qualitatively and quantitatively analyzed via microscopy and a water-soluble tetrazolium salt assay kit, respectively. Alkaline phosphatase activity was assessed and an anthraquinone dye for calcium deposit evaluation was performed to determine osteogenic differentiation. The expressions of (runt-related transcription factor 2) and collagen 1 were also determined via quantitative PCR. Spherical shapes were formed using concave microwells on day 1, which were maintained up to day 21. On day 1, the relative cell viability of 0, 10 and 100 ng/ml BMP-2 treated cells was 100.0±1.9, 97.3±4.4 and 101.3±2.6%, respectively. Significantly higher values for alkaline phosphatase activity were determined in the 100 ng/ml treated group when compared with the control group. Additionally, Runx2 mRNA levels were significantly higher in the 100 ng/ml BMP-2 group compared with the control group, as determined via quantitative PCR. The results of the present study indicated that BMP-2 enhanced the differentiation of stem cell spheres, which was demonstrated by increased alkaline phosphatase activity and Runx2 expression.

Osteogenic effects of bioabsorbable magnesium implant in rat mandibles and in vitro

BACKGROUND

Bone augmentation or grafting is often required for placement of dental implants or surgical reconstruction of bony defects. Bioabsorbable magnesium implant was shown to promote osteogenesis in long bones. The objectives of this study were to determine osteogenic effects of pure magnesium (Mg) in rat mandible and underlying mechanisms.

METHODS

Pure Mg was implanted in sockets after rat mandibular incisors were extracted. Titanium (Ti) was used as control. Systemic effects were determined by serum Mg level and histologic analyses of liver and kidney. Local Mg concentration was measured by microscopy-energy-dispersive spectroscopy (SEM-EDS). Alveolar bone was analyzed by micro-computed tomography (micro-CT) and histology. Osteogenic effects of 0.8 to 20 mM magnesium chloride (MgCl₂ ) on periosteum-derived cells (PDCs) were evaluated by proliferation, alizarin red staining and quantitative RT-PCR assays.

RESULTS

Systemic effects were similar in Mg and Ti groups. Higher local Mg concentration was detected in Mg group (P < 0.05). Micro-CT showed higher alveolar bone volume (2- and 6-weeks post-operation) and denser cancellous bone (2 weeks post-operation) in Mg group, with significant amount of new subperiosteal bone formation on lateral alveolar bone surfaces by H&E staining. In PDC culture, proliferation rates, osteogenic gene expression for runt related transcription factor 2 (Runx2), bone sialoprotein (Bsp) and osteocalcin (Ocn), as well as calcium nodule formation rose significantly in 5, 10, and 20 mM MgCl₂ groups.

CONCLUSIONS

Rapid osteogenesis (especially subperiosteal) is induced by pure Mg in rat mandibular alveolar bone. Osteogenic capacity of PDCs is enhanced by higher Mg ion concentrations in vitro.

Collagen/Chitosan Functionalization of Complex 3D Structures Fabricated by Laser Direct Writing via Two-Photon Polymerization for Enhanced Osteogenesis

The fabrication of 3D microstructures is under continuous development for engineering bone substitutes. Collagen/chitosan (Col/CT) blends emerge as biomaterials that meet the mechanical and biological requirements associated with bone tissue. In this work, we optimize the osteogenic effect of 3D microstructures by their functionalization with Col/CT blends with different blending ratios. The structures were fabricated by laser direct writing via two-photons polymerization of IP-L780 photopolymer. They comprised of hexagonal and ellipsoidal units 80 µm in length, 40 µm in width and 14 µm height, separated by 20 µm pillars. Structures’ functionalization was achieved via dip coating in Col/CT blends with specific blending ratios. The osteogenic role of Col/CT functionalization of the 3D structures was confirmed by biological assays concerning the expression of alkaline phosphatase (ALP) and osteocalcin secretion as osteogenic markers and Alizarin Red (AR) as dye for mineral deposits in osteoblast-like cells seeded on the structures. The structures having ellipsoidal units showed the best results, but the trends were similar for both ellipsoidal and hexagonal units. The strongest osteogenic effect was obtained for Col/CT blending ratio of 20/80, as demonstrated by the highest ALP activity, osteocalcin secretion and AR staining intensity in the seeded cells compared to all the other samples.

Recent Advances in Mechanically Loaded Human Mesenchymal Stem Cells for Bone Tissue Engineering

Large bone defects are a major health concern worldwide. The conventional bone repair techniques (e.g., bone-grafting and Masquelet techniques) have numerous drawbacks, which negatively impact their therapeutic outcomes. Therefore, there is a demand to develop an alternative bone repair approach that can address the existing drawbacks. Bone tissue engineering involving the utilization of human mesenchymal stem cells (hMSCs) has recently emerged as a key strategy for the regeneration of damaged bone tissues. However, the use of tissue-engineered bone graft for the clinical treatment of bone defects remains challenging. While the role of mechanical loading in creating a bone graft has been well explored, the effects of mechanical loading factors (e.g., loading types and regime) on clinical outcomes are poorly understood. This review summarizes the effects of mechanical loading on hMSCs for bone tissue engineering applications. First, we discuss the key assays for assessing the quality of tissue-engineered bone grafts, including specific staining, as well as gene and protein expression of osteogenic markers. Recent studies of the impact of mechanical loading on hMSCs, including compression, perfusion, vibration and stretching, along with the potential mechanotransduction signalling pathways, are subsequently reviewed. Lastly, we discuss the challenges and prospects of bone tissue engineering applications.

Interaction of material stiffness and negative pressure to enhance differentiation of bone marrow-derived stem cells and osteoblast proliferation

Negative pressure wound therapy (NPWT) results in improved wound repair and the combined use of NPWT with elastomeric materials may further stimulate and accelerate tissue repair. No firmly established treatment modalities using both NPWT and biomaterials exist for orthopedic application. The goal of this study was to investigate the response of osteoblasts and bone marrow-derived mesenchymal stem cells to negative pressure and to determine whether a newly developed elastic osteomimetic bone repair material (BRM), a blend of type I collagen, chondroitin 6-sulfate, and poly (octanediol citrate) could enhance the osteoblastic phenotype. The results indicate that proliferation and alkaline phosphatase activity of hFOB1.19 osteoblasts were significantly increased with exposure to 12 hr of negative pressure (-125 mmHg). Follow-on studies with rat and human mesenchymal stem cells confirmed that negative pressure enhanced osteoblastic maturation. In addition, a significant interaction of negative pressure and electrospun BRM resulted in increased mRNA expression of alkaline phosphatase, osteopontin, collagen1α2, and HIF1α, whereas little or no effect on these genes was observed on electrospun collagen or tissue culture plastic. Together, these results suggest that the use of this novel biomaterial, BRM, with NPWT may ultimately translate into a safe and cost-effective clinical application to accelerate bone repair.

Morpholino-functionalized phosphorus dendrimers for precision regenerative medicine: osteogenic differentiation of mesenchymal stem cells

A novel bioactive macromolecule based on morpholino-functionalized phosphorus dendrimers (generation 2, G2-Mor⁺) was developed for osteogenic differentiation of mesenchymal stem cells (MSCs). Interestingly, through in vitro tests, it was shown that G2-Mor⁺ dendrimer can strongly promote the transformation of MSCs into osteoblasts, which implies the potential application of phosphorus dendrimers in bone regeneration for precision regenerative medicine.

Biological evaluation of porous nanocomposite scaffolds based on strontium substituted β-TCP and bioactive glass: An in vitro and in vivo study

In the current study, in vitro analysis of the osteogenic potential of different scaffolds based on strontium-substituted β-TCP (Sr-TCP) and bioactive glass (BG) ceramics was conducted using rabbit bone marrow-derived mesenchymal stem cells (rBMSCs) and the osteogenic ability of the prepared Sr-TCP and BG scaffold was evaluated through alkaline phosphatase activity, mineral deposition by Alizarin red staining, and osteoblastic gene expression experiments. The obtained in vitro results revealed that among experimental Sr-TCP/BG nanocomposite scaffold samples with the composition of Sr-TCP/BG: 100/0, 50/50, 75/25, and 25/75, the 50Sr-TCP/50BG sample presented better osteoinductive properties. Therefore, the optimized 50Sr-TCP/50BG nanocomposite scaffold was chosen for further in vivo experiments. In vivo implantation of 50Sr-TCP/50BG scaffold and hydroxyapatite (HA)/TCP granules in a rabbit calvarial defect model showed slow degradation of 50Sr-TCP/50BG scaffold and high resorption rate of HA/TCP granules at 5 months' post-surgery. However, the 50Sr-TCP/50BG scaffolds loaded by mesenchymal stem cells (MSCs) were mainly replaced with new bone even at 2 months post-implantation. Based on the obtained engineering and biological results, 50Sr-TCP/50BG nanocomposite scaffold containing MSCs could be considered as a promising alternative substitute even for load-bearing bone tissue engineering applications.

Bioreactors Design, Types, Influencing Factors and Potential Application in Dentistry. A Literature Review

Objectives:

A variety of bioreactors and related approaches have been applied to dental tissues as their use has become more essential in the field of regenerative dentistry and dental tissue engineering. The review discusses the various types of bioreactors and their potential application in dentistry.

Methods:

Review of the literature was conducted using keywords (and MeSH) like Bioreactor, Regenerative Dentistry, Fourth Factor, Stem Cells, etc., from the journals published in English. All the searched abstracts, published in indexed journals were read and reviewed to further refine the list of included articles. Based on the relevance of abstracts pertaining to the manuscript, full-text articles were assessed.

Results:

Bioreactors provide a prerequisite platform to create, test, and validate the biomaterials and techniques proposed for dental tissue regeneration. Flow perfusion, rotational, spinner-flask, strain and customize-combined bioreactors have been applied for the regeneration of bone, periodontal ligament, gingiva, cementum, oral mucosa, temporomandibular joint and vascular tissues. Customized bioreactors can support cellular/biofilm growth as well as apply cyclic loading. Center of disease control & dip-flow biofilm-reactors and micro-bioreactor have been used to evaluate the biological properties of dental biomaterials, their performance assessment and interaction with biofilms. Few case reports have also applied the concept of in vivo bioreactor for the repair of musculoskeletal defects and used customdesigned bioreactor (Aastrom) to repair the defects of cleft-palate.

Conclusions:

Bioreactors provide a sterile simulated environment to support cellular differentiation for oro-dental regenerative applications. Also, bioreactors like, customized bioreactors for cyclic loading, biofilm reactors (CDC & drip-flow), and micro-bioreactor, can assess biological responses of dental biomaterials by simultaneously supporting cellular or biofilm growth and application of cyclic stresses.

Bony Regrowth After Deep Lateral Orbital Decompression

PURPOSE

To report on 2 cases of late bony regrowth with clinically apparent proptosis after deep lateral orbital decompression for thyroid orbitopathy.

METHODS

A retrospective review of 2 cases identified by the authors as having late bony regrowth. The authors review the clinical, historical, radiologic, and anatomical findings and discuss the significance thereof.

RESULTS

Bony regrowth with bowing toward the middle cranial fossa is observed at postoperative month 8 in the first case. Cortical bone and marrow was observed to regrow at 2 years postoperatively in the second case. Both patients underwent successful repeat deep lateral orbital decompression with resolution of proptosis and clinical symptoms.

CONCLUSIONS

Late bony regrowth should be considered as a possible cause of recurrent proptosis after orbital decompression in thyroid eye disease.

Evaluation of the Bone Regeneration Effect of Recombinant Human Bone Morphogenic Protein-2 on Subperiosteal Bone Graft in the Rat Calvarial Model

The aim of this study was to evaluate the bone regeneration effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on a subperiosteal bone graft in a rat model. A subperiosteal space was made on the rat calvarium, and anorganic bovine bone (ABB), ABB/low bone morphogenetic protein (BMP) (5 µg), and ABB/high BMP (50 µg) were grafted as subperiosteal bone grafts. The new bone formation parameters of bone volume (BV), bone mineral density (BMD), trabecular thickness (TbTh), and trabecular spacing (TbSp) were evaluated by microcomputed tomography (µ-CT), and a histomorphometric analysis was performed to evaluate the new bone formation area. The expression of osteogenic markers, such as bone sialoprotein (BSP) and osteocalcin, were evaluated by immunohistochemistry (IHC). The ABB/high BMP group showed significantly higher BV than the ABB/low BMP (p = 0.004) and control groups (p = 0.000) and higher TbTh than the control group (p = 0.000). The ABB/low BMP group showed significantly higher BV, BMD, and TbTh than the control group (p = 0.002, 0.042, and 0.000, respectively). The histomorphometry showed significantly higher bone formation in the ABB/low and high BMP groups than in the control group (p = 0.000). IHC showed a high expression of BSP and osteocalcin in the ABB/low and high BMP groups. Subperiosteal bone grafts with ABB and rhBMP-2 have not been studied. In our study, we confirmed that rhBMP-2 contributes to new bone formation in a subperiosteal bone graft with ABB.

Corticotomy for orthodontic tooth movement

Corticotomy was introduced as a surgical procedure to shorten orthodontic treatment time. Corticotomy removes the cortical bone that strongly resists orthodontic force in the jaw and keeps the marrow bone to maintain blood circulation and continuity of bone tissues to reduce risk of necrosis and facilitate tooth movement. In the 21st century, the concept of regional acceleratory phenomenon was introduced and the development of the skeletal anchorage system using screw and plate enabled application of orthopedic force beyond conventional orthodontic force, so corticotomy has been applied to more cases. Also, various modified methods of minimally invasive techniques have been introduced to reduce the patient's discomfort due to surgical intervention and complications after surgery. We will review the history of corticotomy, its mechanism of action, and various modified procedures and indications.

Involvement of bone morphogenetic protein-related pathways in the effect of aucubin on the promotion of osteoblast differentiation in MG63 cells

Aucubin, an iridoid glycoside found in several plants, such as Eucommia ulmoide and Rehmannia, has various pharmacological effects. Bone formation is a complex process in which osteoblast differentiation plays an important role. This study aimed to investigate the promotion effects of aucubin on osteoblast differentiation in MG63 cells, a human osteoblast-like cell line. Aucubin not only improved osteoblast differentiation, as shown by enhanced ALP (alkaline phosphatase) concentration and mineralization in cells, but increased the expression of various cytokines, including collagen I, osteocalcin, osteopontin, integrin β1, and Osterix. Aucubin strongly enhanced the levels of BMP2 (bone morphogenetic proteins-2) in MG63 cells, which play a central role during osteoblast differentiation. Further data show that aucubin exposure after 1 day, 7 days, and 14 days enhanced the expression of Smad1, 5, and 8, and the phosphoresced levels of MAPKs (mitogen-activated protein kinases) family Erk (extracellular signal-regulated kinases), JNK (c-Jun-NH2-terminal kinases), P38, and Akt (serine/threonine protein kinase)/mTOR (mammalian target of rapamycin)/p70s6k in MG63 cells. This study shows the improved effects of aucubin on osteoblast differentiation in MG63 cells, related to the signaling of BMP2-mediated Smads (drosophila mothers against decapentaplegic proteins), MAPKs, and Akt/mTOR/p70S6K. This study indicates the potential of aucubin for osteoporosis treatment.